Development of Fe-doped amorphous nanosilica from Philippine waste rice hull as anode material for lithium battery

Abstract

Silica or silicon dioxide (SiO2) is an indispensable material in many industrial applications. The increasing use of silicon-based material in the development of anode electrodes for batteries is owed to the high theoretical capacity of silicon. The problem of silicon's large volume change upon lithiation can be circumvented by obtaining an amorphous structure in its oxide form and reducing the particle size to nano-size particles. On the other hand, silicon oxide electronic conductivity can be improved by doping or incorporating an electronically conductive material like iron. Furthermore, the development of cheap anode material for lithium (Li) batteries using silica from waste rice hull (RH) is sustainable and a promising approach. In the present study, the microstructure of the iron-doped amorphous nanosilica (Fe-doped AnS) synthesized from Philippine waste RH (PWRH) and its initial electrochemical performance as an anode material for Li batteries were investigated. Properties of the Fe-doped AnS material were characterized using Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS), X-ray Diffraction (XRD), and Fourier Transform Infrared (FTIR). Results of the SEM-EDS and XRD analyses of the Fe-doped AnS revealed the presence of amorphous silica (SiO2), amorphous carbon (C), and maghemite (γ-Fe2O3) structure with a homogeneous distribution of the elements as suggested by EDS. FTIR spectra revealed the occurrence of the different absorption bands of the synthesized material while the galvanostatic discharge-charge performance of the Fe-doped AnS working electrode revealed a specific capacity of 1,232 mAh/g upon lithiation and 8 mAh/g upon delithiation. The resulting lithiation capacity of the prepared battery cell is almost four times more as compared to the commercial graphite anode material. These results suggest that AnS synthesized from cheap and abundant PWRH can be promising anode material for Li batteries.